1. Technical Field
Fuel economy modification in hybrid electric vehicles.
2. Background Art
A hybrid electric vehicle (HEV) typically includes an engine, such as an internal combustion engine (ICE), and an electric motor. For example, the HEV may be a series hybrid electric vehicle (SHEV), a parallel hybrid electrical vehicle (PHEV), or a parallel/series hybrid electric vehicle (PSHEV).
The series hybrid electric vehicle (SHEV) is a vehicle with an engine (most typically an ICE) connected to an electric machine, which provides electric power to a battery. Another electric machine called a traction motor is powered by the battery. The traction motor in the SHEV is the sole source of wheel torque. There is no mechanical connection between the engine and the drive wheels.
The parallel hybrid electrical vehicle (PHEV) has an engine (most typically an ICE) and an electric motor that work together to provide traction wheel torque to drive the vehicle. In addition, the motor in the PHEV can be used as a generator to recover regenerative power to charge the battery.
The parallel/series hybrid electric vehicle (PSHEV) has characteristics of both PHEV and SHEV configurations and is sometimes referred to as a “split” parallel/series configuration. In one of several types of PSHEV configurations, the engine is mechanically coupled to two electric machines in a planetary gear-set transaxle. A first electric machine, the generator, is connected to a sun gear. The engine is connected to a planetary carrier. A second electric motor, a traction motor, is connected to a ring (output) gear via additional gearing in a transaxle. The generator can also contribute to the necessary wheel (output shaft) torque.
During operation of a HEV, the ICE consumes fuel and produces undesirable engine emissions. However, it may be desirable or necessary to increase fuel efficiency of the HEV as well as reduce the amount of undesirable engine emissions as the HEV is operated. Furthermore, it may be desirable or necessary to control the fuel consumption in the HEV to compensate for vehicle-to-vehicle variability, vehicle aging, and calibration inaccuracies in the HEV powertrain.